PROJECT SUMMARY The role of horizontal gene transfer in eukaryotic evolution remains one of the most hotly debated topics in evolutionary biology. While several claims of massive horizontal transfer in eukaryotes have been disproven in recent years, rotifers of the class Bdelloidea, with 8-10% of their genes coming from non-metazoan sources, remain the only metazoan taxon that withstands the scrutiny. Our work has confirmed the presence and functionality of a non-canonical system of epigenetic modification of bacterial origin, capable of introducing bacterial modification marks into eukaryotic DNA. Further, we identified genes of foreign origin that may serve as potential sources of diversification in the expanded system of secondary metabolism. Finally, with desiccation no longer suspected as the leading reason defining the unusual ability of bdelloids to capture foreign genetic material, we are investigating novel types of giant transposable elements that may have participated in gene transfer. These lines of investigation will be pursued and combined to uncover the complex evolutionary history of foreign gene acquisition and diversification in this exceptional metazoan taxon, and to better understand how the barriers preventing such acquisition in most eukaryotic taxa can occasionally be broken in selected branches of the metazoan tree of life. !